Feline
My cat has diabetes and might also have Cushing's disease. What is that?
Cushing's disease, or hyperadrenocorticism, is a rare disorder in cats. It results from the adrenal glands producing abnormally high levels of glucocorticoid hormones (steroids). These excessive steroid levels cause a number of disorders, including impairment of the immune system, skin fragility and impaired ability to heal wounds, profound resistance to insulin (which in turn causes diabetes mellitus), and heart disease. Most affected cats will have a tumor of the pituitary gland in the brain that produces a hormone that in turn causes the adrenal glands to become hyperplastic (develop excess hormone-producing tissue). A few affected cats will have tumors of the adrenal glands that produce the excess glucocorticoids. Cushing's disease in felines tends to occur more often in older and female cats.
Since most cats with Cushing's disease will develop severe diabetes early in the disease process, early signs of Cushing's disease in cats are actually the signs of diabetes mellitus -- excessive thirst and drinking, excessive eating and excessive urination. The diabetes requires high doses of injectable insulin to control. In addition to signs of diabetes, affected cats have very thin and fragile skin, muscle wasting and weakness, a potbelly, hair loss, and depression. Affected cats may gain or lose weight, depending on the interplay of their diabetes and hyperadrenocorticism.
Diagnosis requires verification of abnormal responses of the adrenal gland or its control network to stimulation or suppression with hormonal compounds. Frequently the adrenal glands will be imaged with ultrasound to look for the less common adrenal tumor or for bilateral (both) enlargement (hyperplasia) of the glands.
Most cats are treated surgically, with bilateral removal of the adrenal glands (adrenalectomy). Cats unfortunately do not appear to tolerate the anti-adrenal medications very well. Additionally, treatment with agents to interfere with the excess adrenal hormones or to block their production has mixed and inconsistent results.
The prognosis for affected cats is guarded. Although maintenance medication to replace the normal amounts of adrenal hormones lost as a result of adrenalectomy may be successfully given, diabetes complications create considerable challenges. Additionally, the surgery in these cats is somewhat high risk: hyperadrenocorticoid and diabetic cats will have impaired healing ability and a diminished ability to fight postoperative infection, a major complication of surgery in cats with these diseases. Since these surgical risk factors all arise from the prolonged effects of the excessive glucocorticoid steroids, early diagnosis and treatment of Cushing's disease would probably improve the prognosis slightly.
You may wish to speak with your veterinarian about the possibility of referral to a veterinary internist for a discussion of diagnostic or treatment options. This is a very challenging problem.
The VetCentric Encyclopedia article on canine Cushing's disease has some useful information on the pathology associated with the excess hormone, but the sections on treatment and prognosis will not apply to cats.
01/29/09
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